Transcript Ectotherms and Endotherms

Ectotherms and
Endotherms
Definitions of Ectotherms and
Endotherms
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ECTOTHERMS are organisms that have a limited
ability to control their body temperature. Their cellular
activities generate little heat. Their body
temperatures rise and fall with ambient temperature
changes. Most organisms are ectotherms. Examples
are plants, all invertebrates, fish, amphibians and
reptiles
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ENDOTHERMS are organisms whose metabolism
generates enough heat to maintain an internal
temperature independent of the ambient
temperature. Birds and mammals are endotherms.
Compare responses of named Australian ectothermic and
endothermic organisms to changes in the ambient temperature and
explain how these responses assist in temperature regulation:
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ECTOTHERM RESPONSES TO CHANGING TEMPERATURE:
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Controlling Exposure: The goanna controls its body exposure to
the sun by sun baking in the cool morning, and staying in shade
during the hot hours.
Hibernation: The bogong moths “hibernate” in hot weather (this
is called aestivation). During summer, they gather in caves, their
metabolism slows and the body temperature drops. This is to
maintain body temperature.
Shelter: The central netted dragon stays in sheltered areas to
avoid extreme heat. They can dig burrows or seek shelter in caves
or crevices. This reduces the effect of heat on their body.
Nocturnal Activity: Brown snakes can change into nocturnal
animals when the temperature becomes very hot. Many desert
animals sleep in burrows during the day and are active at night, to
escape the heat.
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ENDOTHERM RESPONSES TO CHANGING
TEMPERATURE:
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Migration: The short-tailed shearwater migrates to
equatorial regions during the winter months. This is to avoid
the cold weather, as the bird only breeds in warm weather.
Insulation: The superb parrot contracts the muscles
controlling its feather in cold conditions, fluffing up its coat.
This maintains a later of trapped air as insulation. This air
reduces heat exchange with the environment.
Evaporation: The red kangaroo licks its arms to cool itself.
The evaporation of the saliva cools its skin.
Nocturnal Behaviour: Hopping mice, and many other
Australian endotherms, are nocturnal. This is to prevent
overheating, and to reduce moisture loss.
Identify some responses of plants to
temperature change:
Plants respond to temperature change by altering
their growth rate – E.G. Some Eucalyptus trees grow
more in spring than in winter.
 In extreme heat or cold, plants can die, but leave
behind dormant seeds.
 Plants may die above the ground, but leave bulbs,
roots, rhizomes or tubers to survive underground.
These then sprout when favourable conditions return
 Some plants can change the orientation of their
leaves in relation to the sun at different times of the
sun, thus controlling temperature
 Leaves hang down vertically to reduce sun exposure
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